1. Field of the Invention
The present invention relates to organic light emitting display devices, and more particularly packaging of the devices.
2. Discussion of Related Art
In recent years, organic light emitting displays have been widely used and are relatively simple. The organic light emitting display is referred to as an organic light emitting device, and is an emissive device using an organic layer as an emission layer. Since the organic light emitting display can eliminate need for a back light as required in a liquid crystal display, it can be made thin and light weight. Thus, the organic light emitting display has been actively developed as a display panel in a portable information terminal such as mobile computer, portable telephone, portable game device, and electronic book.
In general, the organic light emitting display has a structure in which at least one organic layer having an emission layer is interposed between a pair of electrodes, namely, a first electrode and a second electrode. The first electrode is formed on a substrate, and functions as an anode to inject holes. An organic layer is formed at an upper portion of the first electrode. The second electrode is formed on the organic layer to face the first electrode, and functions as a cathode to inject electrons.
When moisture or oxygen from ambient environment is introduced in a device, the life of such an organic light emitting display is reduced, emission efficiency is deteriorated, and emission color changes due to oxidation and peeling. Therefore, in manufacturing the organic light emitting display, it is well known that the device is separate and sealed from an outside to prevent moisture from infiltrating into it. In the sealing method, after organic macromolecule such as polyester (PET) is laminated at an upper portion of the organic light emitting display, or a cover or a cap is formed by a glass or a metal having absorbent, the inside thereof is filled with nitrogen gas. Then, edges of the cover or the cap are capsule-sealed by a sealant such as epoxy.
However, it is impossible for the conventional method to prevent the introduction of device destructive factors such as moisture or oxygen from an outside by 100%. Consequently, a structure of the device is disadvantageous to be applied to an active surface emitting type organic light emitting display weak to moisture, and a process to embody such a method is complicated. In order to solve the aforementioned problems, a capsule sealing method is devised to enhance an adhesion between a device substrate and a cap using a frit as a sealant. U.S. Pat. No. 6,998,776 B2 discloses a structure of sealing an organic light emitting display by coating a frit at a glass substrate.